Java example source code file (Page.java)

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Java - Java tags/keywords

bug, indexoutofboundsexception, page, pagecache, runtimeexception

The Page.java Java example source code

/*
 * Copyright (c) 2000, 2003, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 *
 */

package sun.jvm.hotspot.debugger;

/** A class representing an arbitrary-sized page which can be linked
    into a list. Used by the PageCache. */

public class Page {
  private long   baseAddress;
  private byte[] data;
  private Page   prev;
  private Page   next;
  private long   unmappedPageLength;

  /** The length of the data[] array implicitly defines the size of the
      page. */
  public Page(long baseAddress, byte[] data) {
    this.baseAddress = baseAddress;
    this.data = data;
  }

  /** This constructor creates an "unmapped" page of the specified
      length. Fetches from this page will cause -1 to be inserted into
      the destination buffer. */
  public Page(long baseAddress, long unmappedPageLength) {
    this.baseAddress = baseAddress;
    this.unmappedPageLength = unmappedPageLength;
  }

  public long getBaseAddress() {
    return baseAddress;
  }

  public long getSize() {
    if (data != null) {
      return data.length;
    } else {
      return unmappedPageLength;
    }
  }

  /** Indicates whether this page is mapped in the remote process's
      address space */
  public boolean isMapped() {
    return (data != null);
  }

  public Page getPrev() {
    return prev;
  }

  public void setPrev(Page prev) {
    this.prev = prev;
  }

  public Page getNext() {
    return next;
  }

  public void setNext(Page next) {
    this.next = next;
  }

  /** Throws IndexOutOfBoundsException if the number of bytes
      requested is greater than the page size, or if the start address
      doesn't fall within the page. There are no guarantees on whether
      any data was actually fetched if an IndexOutOfBoundsException is
      thrown. If this page is unmapped, -1 is returned for all
      addresses on this page. */
  public void getData(long startAddress, long numBytes,
                      int[] destBuf, long destBufOffset)
    throws IndexOutOfBoundsException {
    int startOffset = (int) (startAddress - baseAddress);
    if ((data == null) &&
        ((startOffset < 0) || ((startOffset + numBytes) > (baseAddress + unmappedPageLength)))) {
      throw new IndexOutOfBoundsException("startAddress = " + startAddress +
                                          ", baseAddress = " + baseAddress +
                                          ", unmappedPageLength = " + unmappedPageLength);
    }
    for (int i = 0; i < (int) numBytes; ++i) {
      if (data != null) {
        destBuf[i + (int) destBufOffset] = ((int) (data[i + startOffset]) & 0x000000FF);
      } else {
        destBuf[i + (int) destBufOffset] = -1;
      }
    }
  }

  /** Throws IndexOutOfBoundsException if the number of bytes
      requested is greater than the page size, or if the start address
      doesn't fall within the page. There are no guarantees on whether
      any data was actually fetched if an IndexOutOfBoundsException is
      thrown. If this page is unmapped, throws a RuntimeException;
      this should be watched for at higher levels. */
  public void getDataAsBytes(long startAddress, long numBytes,
                             byte[] destBuf, long destBufOffset)
    throws IndexOutOfBoundsException {
    long startOffset = startAddress - baseAddress;
    if (data == null) {
      throw new RuntimeException("Bug in PageCache; should not fetch from unmapped pages using getDataAsBytes");
    }
    System.arraycopy(data, (int) startOffset, destBuf, (int) destBufOffset, (int) numBytes);
  }

  public boolean getBoolean(long address) {
    return (getByte(address) != 0);
  }

  public byte getByte(long address) {
    return data[(int) address - (int) baseAddress];
  }

  public short getShort(long address, boolean bigEndian) {
    int start = (int) address - (int) baseAddress;
    if (bigEndian) {
      return (short)
        (((data[start + 1] & 0xFF)) |
         ((data[start]     & 0xFF) << 8));
    } else {
      return (short)
        (((data[start + 1] & 0xFF) << 8) |
         ((data[start]     & 0xFF)));
    }
  }

  public char getChar(long address, boolean bigEndian) {
    return (char) getShort(address, bigEndian);
  }

  public int getInt(long address, boolean bigEndian) {
    int start = (int) address - (int) baseAddress;
    if (bigEndian) {
      return
        ((data[start + 3] & 0xFF))       |
        ((data[start + 2] & 0xFF) << 8)  |
        ((data[start + 1] & 0xFF) << 16) |
        ((data[start]     & 0xFF) << 24);
    } else {
      return
        ((data[start + 3] & 0xFF) << 24) |
        ((data[start + 2] & 0xFF) << 16) |
        ((data[start + 1] & 0xFF) << 8)  |
        ((data[start]     & 0xFF));
    }
  }

  public long getLong(long address, boolean bigEndian) {
    int start = (int) address - (int) baseAddress;
    if (bigEndian) {
      return
        ((data[start + 7] & 0xFFL))       |
        ((data[start + 6] & 0xFFL) << 8)  |
        ((data[start + 5] & 0xFFL) << 16) |
        ((data[start + 4] & 0xFFL) << 24) |
        ((data[start + 3] & 0xFFL) << 32) |
        ((data[start + 2] & 0xFFL) << 40) |
        ((data[start + 1] & 0xFFL) << 48) |
        ((data[start]     & 0xFFL) << 56);
    } else {
      return
        ((data[start + 7] & 0xFFL) << 56) |
        ((data[start + 6] & 0xFFL) << 48) |
        ((data[start + 5] & 0xFFL) << 40) |
        ((data[start + 4] & 0xFFL) << 32) |
        ((data[start + 3] & 0xFFL) << 24) |
        ((data[start + 2] & 0xFFL) << 16) |
        ((data[start + 1] & 0xFFL) << 8)  |
        ((data[start]     & 0xFFL));
    }
  }

  public float getFloat(long address, boolean bigEndian) {
    return Float.intBitsToFloat(getInt(address, bigEndian));
  }

  public double getDouble(long address, boolean bigEndian) {
    return Double.longBitsToDouble(getLong(address, bigEndian));
  }
}